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<head>
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    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        a:link{
            display: block;
            width: 93px;
            height: 29px;
            background-image: url(../img/4.png);
            /* 4.png是按钮图片 */
        }
        a:hover{
            background-image: url(../img/5.png);
            /* 5.png是鼠标移入时的按钮图片 */
        }
        a:active{
            background-image: url(../img/6.png);
            /* 6.png是点击时的按钮图片 */
        }
        /* 三张图片容易出现缓存问题 */
    </style>
</head>
<body>
    <a href="javascript:"></a>
</body>
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